1. Field of the Invention
The present invention generally relates to a control mechanism for an engine valve. More particularly, this invention pertains to an improved mechanism for controlling the timing of the intake and exhaust valves in an internal combustion engine.
2. Related Art
An internal combustion engine in a vehicle, generally requires a control mechanism for controlling the timing for the opening and closing of the intake and exhaust valves, in relation to the operation state of the engine. The control mechanism conveys and regulates the rotational phase of a camshaft with respect to a crank shaft.
A control mechanism for engine valve timing of this type is disclosed in the Japanese Unexamined Patent Publication No. 61-279713. This Publication describes a timing pulley 101 which is operatively connected to the engine, and which is disposed at one end of a camshaft 100. A helical ring gear 102 interconnects the camshaft 100 and the timing pulley 101. At least one set of teeth is formed on the inner and outer peripheries of the ring gear 102. When the ring gear 102 moves along the axial direction, it rotates in synchrony with the camshaft 100. Pressurized oil is supplied through oil passages in the camshaft 100, by means of a hydraulic pump within the timing pulley 101. One end section of the ring gear 102 is supported by a spring 103 for withstanding the oil pressure.
When oil pressure is applied on the ring gear 102, the ring gear 102 is caused to move in the axial direction and to overcome the resistive force of the spring 103. Torsion against the timing pulley 101 is generated on the camshaft 100, so that a phase in the rotational direction (the rotational phase), between the camshaft 100 and the timing pulley 101 is changed, for regulating the opening and closing timing of the intake and exhaust valves. The ring gear 102 is moved along the axial direction of the camshaft 100 in order to vary the value of the phase shift. When it is desired to increase the rotational phase, it would be necessary to lengthen the stroke of the ring gear 102, or to increase the teeth angle of the ring gear 102.
When it is desired to lengthen the stroke of the ring gear 102, the size of the control mechanism is increased along the axial direction. Therefore, the mounting of the control mechanism in a vehicle becomes more difficult. When the torsion angle of the teeth is increased, the operative resistance of the ring gear 102 is increased. Therefore, in order to increase the hydraulic pressure, the operative response time of the mechanism should be decreased.